Crimped polyester-yarn from cold drawn polyester-POY-yarn and process for its manufacture

ABSTRACT

PCT No. PCT/CH83/00138 Sec. 371 Date Aug. 9, 1984 Sec. 102(e) Date Aug. 9, 1984 PCT Filed Dec. 8, 1983 PCT Pub. No. WO84/02357 PCT Pub. Date Jun. 21, 1984.The invention concerns a crimped Polyester-yarn obtained from cold drawn Polyester-POY as well as a process for its manufacture. For this yarn the stress/strain course between 10 and 30% elongation resulting from the stretch test corresponds to a secant modul of 0-100%. Application in the knitting, weaving and warp knitting.

The invention concerns a crimped Polyester-yarn obtained from cold drawnPolyester-POY as well as a process for its manufacture and theapplication of such yarns.

The DE-AS No. 12 91 852 concerns a process for the manufacture offibres, yarns or films from crystallizable Polyester, by slow meltspinning, subsequently warm drawing and after that thermal shrinkage ofthe yarns or films. The thus obtained fibres, yarns of films may beirreversible lengthened by moderate heat treatment, without that atension is exercised on them, and they no more return on their originallength by cooling and drying.

The cold drawing of Polyester-POY (=Partially Oriented Yarn) is not veryspread. But nevertheless it is known: TEIJIN mentions in the JapaneseApplication No. 0 055 268 of 16.5.77 the cold drawing in a draw ratio of1.05-1.35 of a Polyester yarn spun between 4000 and 7000 m/min. Theliterature does not mention the possibility of aftertreatment of suchyarns. The present invention concerns a new yarn, which is manufacturedby an aftertreatment of a cold drawn Polyester-POY.

The invention concerns a crimped Polyester-yarn, obtained from colddrawn Polyester-POY-yarn, characterised in that the stress/strain coursebetween 10 and 30% elongation resulting from the stretch testcorresponds to a secant modulus of 0-100%.

We designate as secant modulus the end value of a straight line, definedby the stress by 10 and 30% elongation, parallel shifted on stress 0 byelongation 0. The unity corresponds to the percentage portion of thebreaking stress by 100% theoretical elongation.

Hereafter the definition of the secant modulus will be preciselyexplained in relation with FIG. 1. It is already possible to mention,that the stress/strain diagram shows a marked plateau zone, whichcharacterises the yarn according to the invention.

These yarns are twistless and totally shrunked. The crimp is threedimensional, optically interesting and presents a fine appearance. Thecrimp of the individual fibrils is irregular.

If here one speaks of Polyester-POY, endless yarns are concerned, whichare spun between 2000 and 5000 m/min. The cold drawing takes place atroom temperature on a draw machine, for example a drawtwist- ordraw-wind machine, with a draw ratio of 1.2 to 2.2. The denier of theindividual filaments is not critical.

The invention further concerns a process for the manufacture of theabove mentioned crimped yarns, by which cold drawn Polyester-POY-yarnsare subjected to a thermal treatment. The thermal treatment is carriedout in the air, vapour or inert liquid. One understands under inertliquid, a liquid, in which Polyester does not dissolve, and which doesnot react with the Polyester. Water is preferred as such a liquid. Theyarn simultaneously shrinks very largely (up to 60%) by the treatment.

The shrinkage force of the cold drawn Polyester-POY-yarn nevertheless isvery small, so that already smallest stresses could reduce or evenprevent the shrinkage. The thermal treatment is therefore carried outtensionless or under controlled overfeed. The overfeed varies between 20and 100%, preferably between 40 and 80%.

The thermal treatment preferably takes place in a shocking way. Undershocking way treatment one understands here a sudden, short-term warmingup of the yarn or by wet treatment a bringing in of the article in thewarmed-up bath.

One works in the air at a temperature of more than 80° C., preferablybetween 140° and 220° C., continuously, under controlled overfeed of20-100%, preferably of 40-80%. A convection heater is advantageouslyused for the thermal treatment of the yarn.

If the thermal treatment is carried out in steam or inert liquid, itoccurs at a temperature of more than 60° C., preferably at 90°-100° C.,tensionless, respectively with a controlled overfeed of 20-100%,preferably of 40-80%. Steam means saturated steam or overheated watersteam.

The crimp of the yarn according to the invention is irregular and stresssensitive. The further processing of the yarn should therefore becarried out under a stress smaller than about 0.5 cN/dtex. This ispossible or normally the case with all present knitting-, weaving- andwarp knitting machines.

The invention further concerns the application of the crimped yarn inthe knitting, weaving and warp knitting.

The invention is precisely explained in relation to the joined figures,which show

FIG. 1 the stress/strain diagram of a yarn according to the invention,as well as the representation of the secant modulus,

FIG. 2 the stress/strain diagram of the raw material and of the yarnaccording to the invention,

FIG. 3 the stress/strain diagram of yarns, which were treated underdifferent overfeed,

FIG. 4 a yarn according to the invention beside a false twist texturedand a flat yarn, and

FIG. 5 the characteristic surface structure of the yarn according to theinvention.

FIG. 1 shows a stress/strain diagram A of a Polyester yarn according tothe invention, half mat, round, tested according to DIN 53834, firstpart. Point 1 gives the breaking stress in Newton, and point 2 thebreaking elongation in %. The yarn is characterised by this plateau zonebetween the points 3 and 4. Defined by point 3 (elongation 10%) andpoint 4 (elongation 30%), a straight line B is drawn, limited byelongation 0 and theoretical elongation 100% (point 5). In order tocalculate the secant modulus according to the invention, the straightline B is parallel shifted on stress 0 by elongation 0. Then, thestraight line C results with secant modulus point 6 by 100% elongation.The thus obtained stress by 100% theoretical elongation is calculated aspart expressed as percentage of the effective breaking stress (point D),in our example s=23.5%.

FIG. 2 shows the curve F of the stress/strain diagram of a cold-drawnPolyester-POY-yarn and the curve G that of a thermal treated yarn. Thetreatment took place in a shocking way, tensionless in warm water.

FIG. 3 shows the stress/strain diagram H and I of the Polyester yarnsaccording to the invention, which were thermally treated by 40respectively 80% overfeed. Both tests took place with Polyester yarns,half mat, round (denier of the cold drawn Polyester-POY dtex 84 f 15) ata temperature of 200° C. As heat device served the convection heater ofa fixing respectively poststabilizing machine. The speed was at 110m/min. The points H₁ and I₁ give a value of the secant modul s=46.4%respectively s=11.3%.

FIG. 4b shows a yarn according to the invention, FIG. 4a a false twisttextured Polyester yarn and FIG. 4c a flat yarn. The irregularity of thecrimp of the individual fibrils is clear evident from FIG. 4b.

FIG. 5 shows a Scanning-Electronic-Microscope photo with a magnificationof 2100:1. On this photo, the typical transverse lines according to theprocess are clear obvious.

The invention is precisely explained in relation to the examples.

EXAMPLE 1 (three steps process)

Polyester-POY dtex 150 f 15 was manufactured at a speed of 3100 m/Min.The drawing took place with a ratio of 1:1.93 at 652 m/min at roomtemperature on a drawtwist-machine.

Subsequently the bobbins were shrunk in a shocking way on a fixing-respectively poststabilizing machine in the convection heater (heatlength 63 cm) at 200° C. The withdrawal speed was at 110 m/min. Thedelivery speed varied between 154 m/min (corresponding to 40 % overfeed,respectively 28.6% shrinkage, FIG. 3 H) and 198 m/min (corresponding to80% overfeed, respectively 44.4% shrinkage, FIG. 3 I). The properties ofthe yarn according to the invention are mentioned in table 1.

                  TABLE 1                                                         ______________________________________                                                    40% overfeed                                                                            80% overfeed                                            ______________________________________                                        secant modulus S (%)                                                                        46,4 (H.sub.1)                                                                            11,3 (I.sub.1)                                      breaking stress (N)                                                                         3,7         3,4                                                 breaking      72          107                                                 elongation (%)                                                                boiling shrinkage                                                                           0,2         +1,8                                                at 98° C. (%)                                                          hot shrinkage +4,3        +11,0                                               at 160° C. (%)                                                         ______________________________________                                         + = extension                                                            

EXAMPLE 2 (two steps process)

Polyester-POY dtex 170 f 36 was manufactured at a speed of 3100 m/min.These bobbins were continuously cold drawn and shrinked in a shockingway. The manufacturing conditions are mentioned in table 2.

                  TABLE 2                                                         ______________________________________                                                      Variant A                                                                              Variant B                                              ______________________________________                                        entering in the 91 m/min   229 m/min                                          draw-zone                                                                     draw-ratio      1:1.75     1:1.75                                             withdrawal      160 m/min  400 m/min                                          convection heater:                                                            temperature of the                                                                            220° C.                                                                           220° C.                                     shrinking zone                                                                length of the heater                                                                          1,20 m     1,20 m                                             overfeed/shrinkage                                                                            60%/37,5%  60%/37,5%                                          winding         100 m/min  250 m/min                                          ______________________________________                                    

The properties of the yarn according to the invention are mentioned intable 3.

                  TABLE 3                                                         ______________________________________                                                       Variant A                                                                             Variant B                                              ______________________________________                                        secant modulus S (%)                                                                           65,6      23,3                                               breaking stress (N)                                                                            3,2       3,9                                                breaking         67        92                                                 elongation (%)                                                                boiling shrinkage                                                                              1,2       +2                                                 at 98° C. (%)                                                          hot shrinkage    +1,5      +9                                                 at 160° C. (%)                                                         ______________________________________                                         + = extension                                                            

The yarns according to the invention are directly used in the knitting,weaving and warp knitting or are twisted and/or sized for example forweaving warp use.

We claim:
 1. Crimped polyester yarn obtained from cold drawnpartially-oriented polyester yarn, said crimped polyester yarn having asecant modulus of 0-100% as determined by the stress versus strain curvefor said crimped polyester yarn between 10% and 30% elongation. 2.Crimped polyester yarn according to claim 1 wherein individual fibrilsof said yarn have an irregular crimp.
 3. Crimped polyester yarnaccording to claims 1 or 2 which is twistless.
 4. Crimped polyester yarnaccording to claims 1 or 2 which is shrunk up to 60% of its unshrunklength.
 5. Crimped polyester yarn according to claim 3 which is shrunkup to 60% of its unshrunk length.